Proteins and protein hydrolysates are frequently used as whipping agent in sugar confectionery products. Protein hydrolysates are preferably used in case whipping power is required while proteins are more preferred when a contribution to the stability is required. Aeration of carbohydrate containing products can be carried out using a number of methods. Methods that are frequently applied in sugar confectionery are:    1) the open batch system,    2) the pressure batch system,    3) the one step continuous system,    4) the two step continuous system.
Protein hydrolysates in general perform well as whipping agent in all four systems when mixtures containing more than 60% (w/w) carbohydrate are aerated. Except for the pressure batch system the whipping performance of hydrolysed proteins in this mixtures is always better than that of egg white proteins.
In the batch pressure system sugar syrup with a temperature in the range of 105–145° C. is added to a premix with the protein or the protein hydrolysate after which the mixture is aerated at elevated pressure (in general 2–4 bar). The aerated mass is collected carefully via an expansion pipe to allow a gradual release of the pressure. Due to the high aeration temperature and the stability requirements during expansion egg white proteins are found to out perform the protein hydrolysates that are currently available on the market.
There are many reports in the literature dealing with the foaming properties of protein hydrolysates. The more recent ones deal with the enzymatic hydrolysis of protein while the older ones (period 1945–1955) deal with the alkaline hydrolysis of proteins. Alkaline milk protein hydrolysates were used in fire extinguisher foams and as egg substitutes in aerated food products (Kumatat and Beeby, Dairy Industries, September 1954).
In U.S. Pat. No. 2,522,050 a process of manufacturing foaming agent is disclosed according to which a protein is subjected to an alkaline hydrolysis in an aqueous solution containing calcium hydroxide and/or magnesium hydroxide at a pH of at least 10 and at a temperature substantially below 100° C. for a period of at least two days, resulting in a product having satisfactory foaming properties. The obtained product is a mixture of protein and polypeptide containing 5–40% polypeptides. As apparent from the description and the examples of U.S. Pat. No. 2,522,050 it is noticed that the term “substantially below 100° C. ” should be interpreted as from room temperature to about 40° C. (see column 2, lines 24–25 and the Examples of U.S. Pat. No. 2,522,050).
The above indicated view with respect to an upper hydrolysing temperature of about 40° C. is supported by the contents of GB 670,413. In said GB 670,413 a process for the preparation of foamable products is disclosed according to which proteins are subjected at ordinary temperature, i.e. about 20–25° C. for a period of at least one day to hydrolysis by an aqueous liquid containing calcium hydroxide. For the sake of completeness it is referred to a passage on page 2, lines 55–60, clearly indicating that the hydrolysation of proteins with alkaline earth hydroxides at temperatures to 100° C. and higher will result in protein solutions not processing satisfactory foaming properties.
It is well known to a man skilled in the art that the poor taste of the alkaline hydrolysates is a serious drawback. In general they are chalky and bitter, and in addition they can have a sulphury and rubbery taste. Increasing the temperature during hydrolysis, which may reduce the reaction time also increases the formation of these unwanted flavour components. As a consequence the reaction temperature is a dictating compromise between the flavour of the product and the economics of producing it and does result in an upper hydrolysing temperature of about 40° C.